Currently I have 4 drives+Parity in my array and I'm planning on adding another one, but I'd like to do some clean up first and I want to make sure this is going to work.

 

Current Layout

Parity 2TB

Disk1 1.5TB (Movies)

Disk2 1.5TB (TV)

Disk3 500GB (MP3)

Disk4 500GB (Misc), (Backup) and a few other shares I can't recall at this time

 

I'd like to move all my MP3 files from Disk3 to Disk4 and then pull Disk3 and swap in a 2TB drive so I can expand my movies more. Can I just simply create another MP3 folder on Disk4 and then move the existing contents from \\tower\Disk3 to \\tower\Disk4 and then change the User Share listing in the control panel to point at Disk4?

 

Currently all my User Shares are Read Only, but I have my Disk Shares set to Hidden-Read/Write

Yes, you can do as you described, though you would need to do it using the disk shares as your user shares are read-only.  However, here is what I would do:

 

1) Preclear the new 2 TB.

2) Swap disk3 with the precleared 2 TB.

3) Wait for unRAID to rebuild the mp3s onto the new 2 TB. (8+ hours)

4) Verify that your mp3s still work (just play a random few, and make sure the total size is correct).

5) Browse into the disk3 (which is now the 2 TB drive) disk share.  Drag and drop the entire mp3 folder onto disk4's disk share using TerraCopy (this will be slow since the copy will happen over the network, but you will gain the advantage of CRC checks after it completes). (probably 5-8 hours)

6) Again, verify that your mp3s still work.

7) Preclear and the 500 GB drive (formally disk3) as disk5, if you wish.

 

This method is quite slow compared to some other options, but the benefit is that if something goes wrong at any point you will still have all your mp3s safely tucked away on the 500 GB drive (currently disk3).  Safety over speed is always my creed.